As uniformity requirements for better yield control are getting tighter and tighter, for example, as moving towards 20 nm node technology and beyond, any residual skew in a plasma reactor will limit reaching the tight specification for etch uniformity. The inventors believe that external magnetic field interference is among the few remaining skew sources that need to be addressed to achieve such a tight uniformity specification.
Thus, the inventors have provided embodiments of improved plasma-enhanced substrate process chambers.